An aforesaid toothbrush is known inter alia from U.S. Pat. No. 4,450,599. In that Patent the main cause of caries and gingivitis is acknowledged to be a lasting formation of dental plaque and an adequate removal of dental plaque is mentioned to be the desired performance of toothbrushing. In order to achieve an adequate removal of dental plaque a duty time above a minimum time and a duty pressure between a minimum and a maximum pressure are acknowledged to be desired. As a consequence the control means of the known toothbrush is provided with the time-measuring means and the pressure-measuring means to determine the duty time and the duty pressure as well as to drive the indication means to inform the user of the duty performance, i.e. the achieved removal of dental plaque. In the known toothbrush, to determine the minimum time and the desired pressure, the time-measuring means is only activated, when the pressure-measuring means determines a duty pressure between the minimum and the maximum pressure, and the indication means is only activated, when the time measuring-means determines a duty time exceeding the minimum time. However, notwithstanding the design and the construction of the known toothbrush, the achieved removal of dental plaque, when the indication means is activated, and the disclosed display of the duty performance are found to be inaccurate.
As a consequence, the present invention has the object to provide an electric toothbrush, which provides an accurate determination and an adequate indication of the duty performance.